Sound reproduction in general may be classified as a process that includes sub-processes. These sub-processes may include one or more of sound capture, sound transfer, sound rendering and other sub-processes. A sub-process may include one or more sub-processes of its own (e.g. sound capture may include one or more of recording, authoring, encoding, and other processes). Various transduction processes may be included in the sound capture and sound rendering sub-processes when transforming various energy forms, for example from physical-acoustical form to electrical form then back again to physical-acoustical form. In some cases, mathematical data conversion processes (e.g. analog to digital, digital to analog, etc.) may be used to convert data from one domain to another, such as, various types of codecs for encoding and decoding data, or other mathematical data conversion processes.
The sound reproduction industry has long pursued mastery over transduction processes (e.g. microphones, loudspeakers, etc.) and data conversion processes (e.g. encoding/decoding). Known technology in data conversion processes may yield reasonably precise results with cost restraints and medium issues being primary limiting factors in terms of commercial viability for some of the higher order codecs. However, known transduction processes may include several drawbacks. For example, audio components, such as, microphones, amplifiers, loudspeakers, or other audio components, generally imprint a sonic type of component colorization onto an output signal for that device which may then be passed down the chain of processes, each additional component potentially contributing its colorizations to an existing signature. These colorizations may inhibit a transparency of a sound reproduction system. Existing system architectures and approaches may limit improvements in this area.
A dichotomy found in sound reproduction may include the “real” versus “virtual” dichotomy in terms of sound event synthesis. “Real” may be defined as sound objects, or objects, with physical presence in a given space, whether acoustic or electronically produced. “Virtual” may be defined as objects with virtual presence relying on perceptional coding to create a perception of a source in a space not physically occupied. Virtual synthesis may be performed using perceptual coding and matrixed signal processing. It may also be achieved using physical modeling, for instance with technologies like wavefield synthesis which may provide a perception that objects are further away or closer than the actual physical presence of an array responsible for generating the virtual synthesis. Any synthesis that relies on creating a “perception” that sound objects are in a place or space other than where their articulating devices actually are may be classified as a virtual synthesis.
Existing sound recording systems typically use a number of microphones (e.g. two or three) to capture sound events produced by a sound source, e.g., a musical instrument and provide some spatial separation (e.g. a left channel and a right channel). The captured sounds can be stored and subsequently played back. However, various drawbacks exist with these types of systems. These drawbacks include the inability to capture accurately three dimensional information concerning the sound and spatial variations within the sound (including full spectrum “directivity patterns”). This leads to an inability to accurately produce or reproduce sound based on the original sound event. A directivity pattern is the resultant object radiated by a sound source (or distribution of sound sources) as a function of frequency and observation position around the source (or source distribution). The possible variations in pressure amplitude and phase as the observation position is changed are due to the fact that different field values can result from the superposition of the contributions from all elementary sound sources at the field points. This is correspondingly due to the relative propagation distances to the observation location from each elementary source location, the wavelengths or frequencies of oscillation, and the relative amplitudes and phases of these elementary sources. It is the principle of superposition that gives rise to the radiation patterns characteristics of various vibrating bodies or source distributions. Since existing recording systems do not capture this 3-D information, this leads to an inability to accurately model, produce or reproduce 3-D sound radiation based on the original sound event.
On the playback side, prior systems typically use “Implosion Type” (IMT), or push, sound fields. The IMT or push sound fields may be modeled to create virtual sound events. That is, they use two or more directional channels to create a “perimeter effect” object that may be modeled to depict virtual (or phantom) sound sources within the object. The basic IMT paradigm is “stereo,” where a left and a right channel are used to attempt to create a spatial separation of sounds. More advanced IMT paradigms include surround sound technologies, some providing as many as five directional channels (left, center, right, rear left, rear right), which creates a more engulfing object than stereo. However, both are considered perimeter systems and fail to fully recreate original sounds. Implosion techniques are not well suited for reproducing sounds that are essentially a point source, such as stationary sound sources (e.g., musical instruments, human voice, animal voice, etc.) that radiate sound in all or many directions.
With these paradigms “source definition” during playback is usually reliant on perceptual coding and virtual imaging. Virtual sound events in general do not establish well-defined interior fields with convincing presence and robustness for sources interior to a playback volume. This is partially due to the fact that sound is typically reproduced as a composite' event reproduced via perimeter systems from outside-in. Even advanced technologies like wavefield synthesis may be deficient at establishing interior point sources that are robust during intensification.
Other drawbacks and disadvantages of the prior art also exist.